A voice mail system (VMS) provides a voice mailbox that allows an inbound voice message to be stored when the user is away from the receiving telephone or in the event a busy signal is encountered by a caller, so that the recipient can learn of the call. The caller may also choose to leave a message directly in the voice mailbox of the recipient of the call when a "live call" is not necessary or desired.
One additional feature of a VMS allows a recipient of an internal call (from another person having an account on the same VMS) to listen to a message stored in his or her voice mailbox and, by operating the keys on a telephone keypad, to initiate a reply to the message. To initiate a reply to the internal message, the recipient does not need to identify the extension of the source of the call because the VMS supplies the source extension. However, an internal call is generally identified by the extension from which the call was placed (source/extension), not the caller. Thus, if the caller did not use his or her own phone, a reply would be sent to the calling extension, not to caller's personal extension.
A receiver can reply with a "live call" to the calling extension by pressing keys on the number pad and being directly connected. Alternatively, a message direct to the voice mail box of the calling extension can be created by pressing the appropriate keys to initiate the reply command; the recipient records the reply message and hangs up; the VMS automatically sends the recorded reply message to the voice mailbox of the calling extension. Again, this reply feature is only available for calls between users having accounts on the same VMS (internal callers), and only when the voice message includes a return voice mailbox address of the original calling location. Recipients of calls from external callers (people external to the VMS), such as cellular phone users, etc., cannot automatically send a reply to such messages since the reply feature cannot identify the source of the call. Rather, the recipient must listen to the message, write down the name and number of the caller and then after hanging up, call back the person who left the message.
Voice messaging also allows internal communication from one caller to multiple recipients on the same VMS system without the caller initiating a call to each individual recipient's voice mailbox.
Two or more VMSs of a similar type may be connected together to operate as a single VMS. The two VMSs can be at different locations. The network may operate through, for example, a dial up (e.g., analog line) connection, or a digital connection (e.g., an Integrated Services Digital Network (ISDN) lines).
Sending messages and replies in a voice message network requires a protocol for communicating between the separate VMS systems. A widely-used protocol for distributing voice messages using analog lines between networked VMS systems is the Audio Messaging Interchange Specification (AMIS), available for analog telephone lines (AMIS-A) or for a digital network (AMIS-D). The AMIS-A protocol distributes messages via a voice dial-up line; Dual Tone Multi Frequency (DTMF) tones are used for signaling.
Individual VMS companies have also developed their own proprietary protocols to use between their own VMS systems. However, due to the proprietary nature, these protocols only work between VMS systems made by the same company; VMS equipment from different companies, each with its own proprietary protocol, are unable to communicate with one another.
Currently, voice message networking does not allow a receiver of a message to automatically reply to caller on a different VMS. Therefore, a person on a VMS can receive an internal message (i.e., from a caller on a same VMS or VMS network) and an external message (i.e., from a different VMS, mobile phone, home phone, etc.), but cannot reply in the same manner to each type of message.
What is needed is a system that allows a recipient to reply to any internal or external voice message in a common manner. Additionally, a system is needed to return a call to an actual caller, not just the location (calling extension) from which the message or call is sent.